Hitherto, this kind of rotary connector has been used as electrical connecting means between a movable element and a stationary element of a steering device of an automobile or the like. In this rotary connector, the rate of flat cable in the total cost is high, and it is attempted to lower the cost by shortening the required length of flat cable. Such prior art is proposed in Japanese Laid-open Patent No. 4-310445.
FIG. 9 is a top sectional view showing a schematic structure of the rotary connector disclosed in this patent publication. As shown in FIG. 9, an inside case is rotatably fitted in an outside case 1, and a flexible flat cable 4 is accommodated in a ring-shaped space 3 formed between the outside case 1 and inside case 2. Ends 4A, 4B of the flat cable 4 are respectively fixed to the outside case 1 and inside case 2, and are connected to an external electric circuit. The flat cable 4 is accommodated in the space 3 as being wound in a reverse direction on the inner side of the outer tube of the outside case 1 and on the outer side of the inner tube of the inside case 2, and the inverted position of this winding direction is the U-shaped inverted portion 4C. In this space 3, moreover, a plurality of rollers 6 coupled along the peripheral direction by a coupling member 5 are disposed, and the inverted portion 4C of the flat cable 4 is guided to be inverted along roller 6A.
In thus constituted rotary connector, when the inside case 2 is rotated in the counterclockwise direction, the inverted portion 4C of the flat cable 4, and the rollers 7 coupled to the coupling member 5 also move in the peripheral direction of the space 3, and the winding state of the flat cable 4 is a rewound state, being wound more on the inner side of the outside case 1. When the inside case 2 is rotated in the clockwise direction, the inverted portion 4C of the flat cable 4, and the rollers 6 coupled to the coupling member 5 also move in the same direction, and the winding state of the flat cable 4 is a tightened state, being wound more on the outer side of the inner tube of the inside case 2.
In such conventional rotary connector, however, in order to control the move of the flexible flat cable 4 in the peripheral direction, a slight clearance is provided between the plurality of rollers 6 coupled by the coupling member 5 and the coupling member 5 in order to allow the rollers 6 to rotate. Moreover, since the rollers 6 are large in mass, due to vibration from outside or automobile or the like, collision sound between the coupling member 5 including the rollers 6 and the inside case 2 or outside case 1, and collision sound due to clearance between the rollers 6 and coupling member 5 were caused, which were heard as noise inside the automobile.
It is hence an object of the invention to solve such problems of the prior art, and present a highly reliable rotary connector reduced in noise level at low cost.